Headline: High level review of a wide range of proposed marine geoengineering techniques

While Marchetti (1977) was the first to propose using ocean density currents to transport and store anthropogenic carbon dioxide in the deep ocean, “marine geoengineering” first came to widespread public attention in 1990 when global headlines announced US ocean scientist John Martin idea that ocean fertilization could be used to enhance biological carbon dioxide uptake and storage to counteract carbon dioxide induced global warming. It came to widespread public attention again in 2007 due to a proposed ocean iron fertilization activity, planned as a commercial venture by Planktos Inc., off the Galapagos Islands. Such ventures have since taken place in the North-East Pacific off Canada and have been planned for the western seaboard of South America off Chile. The Contracting Parties to the London Convention and London Protocol (LC/LP) expressed concern about the marine environmental impacts of the proposed activity off the Galapagos. In 2008 the Parties adopted a resolution deciding that ocean fertilization activities other than legitimate scientific research should be considered as contrary to the aims of both instruments. Subsequently, due to ongoing interest in marine geoengineering, the LP was amended in 2013 to regulate ocean fertilization activities. These amendments also enable the Parties to regulate other marine geoengineering activities within the scope of the LP by listing them in the new Annex 4 of the Protocol. Thus, the LP has a governance framework that potentially can be applied to newly emerging marine geoengineering technologies. Objectives In the light of the growing interest in marine geoengineering techniques and the LP amendment, GESAMP decided that a Working Group (WG) was needed to: 1 Better understand the potential environmental (and socio-economic) impacts of different marine geoengineering approaches; and 2 Provide advice to the London Protocol Parties to assist them in identifying those marine geoengineering techniques that it might be sensible to consider for listing in the new Annex 4 of the Protocol. Establishment of WG 41 The WG was established and comprised mainly natural scientists with wide-ranging expertise relevant to marine geoengineering, along with a smaller group of experts from economics and political sciences. The preliminary and main findings are reported here.